More often than not, growers focus on the basic necessities for plant growth that are easily controlled: light, water, temperature and plant nutrients. Just because air cannot be seen, does not mean that it is not a critical element in the growth and development of plants. The benefits of increasing carbon dioxide (CO2) levels for the leaves, flowers, and fruits of plants is well understood, but often overlooked are the air levels in the form of oxygen (O2) that can drastically affect plant growth and development.
Factors that contribute to oxygen levels in the plant root zone can be affected by the physical characteristics of the growing substrate, the temperature of the root zone or nutrient solution, and the frequency of irrigation (watering).
The primary physical characteristics that can influence the oxygen levels of a growing substrate are water holding capacity and particle size determining pore space. If the water holding capacity is very high, such as in a peat-based substrate, the growing medium will retain higher than optimal levels of water versus available oxygen essentially suffocating the plant roots. The particle size of a growing media will determine the amount of space between the particles, which affects the amount of free oxygen in the rhizosphere (root zone). The more compacted and moist the growing media is, the less oxygen the plant roots have the potential to absorb.
The temperature of the root zone or the nutrient solution will affect the amount of free oxygen for plant roots. While there are various plants that thrive in different environments, most cultivated plants have an optimal root zone temperature between 65-75° F. At temperatures above and below this optimal range, the uptake of both water and plant nutrients is decreased due to limited oxygen to the plant roots.
The frequency and amount of nutrient solution or water applied to the plant root zone is also related to oxygen availability for plant roots. Determining the optimal amount and timing of irrigation is a balancing act that is dependent on the water holding capacity of the growing medium, the size of the plant being grown, and the temperature of the growing environment. Keeping an eye on these factors will allow a grower to maximize oxygen levels and increase plant growth.
– Alex Schroeder and Brandon Jewell